Cap and Trade vs. Taxes

In the beginning, economists touted emissions taxes and cap-and-trade systems as efficient, market-friendly methods for reducing pollution. The idea: put a price on pollution equal to the damage it caused or decide what level of emissions was acceptable to society as a whole, and then let businesses decide how to minimize the cost. The two approaches – put a price on emissions or put a limit their total quantity — were thought to be equivalent means to the same end.

Then came Martin Weitzman, a very clever economist from Harvard, who showed decades ago that the choice between the price and quantity approaches mattered a lot when policymakers weren’t certain what the costs and/or benefits of pollution control would be. And now Round Three: In a recent, provocative piece [Download Here], David Weisbach of the University of Chicago questions Weitzman’s conclusions. He concludes that the optimal approach may change if you make the (realistic) assumption that policymakers can alter course in response to new information.

And then there’s another factor to consider: the systems can be designed to look a lot like each other. For example, a cap-and-trade system with a “safety valve,’’ which effectively limits the maximum market price of emissions permits, in many respects mimics the impact of an emissions tax.

So where does that leave us on climate change policy? The key is not to get lost in the trees – any market-based system that rewards people and businesses for emitting less carbon would be a big step forward.